Russia's Foreign Ministry has expressed its "regret" over an assault on a senior Dutch diplomat in his Moscow apartment.

The deputy head of the Netherlands' Mission in Moscow, Onno Elderenbosch, was said not to have been seriously injured in the attack, which started when two men arrived at his apartment claiming to be electricians.

Officials said the assailants used lipstick to write "LGBT" -- shorthand for lesbian, gay, bisexual, and transgender -- on a mirror before escaping. The Dutch Foreign Ministry in The Hague has summoned the Russian ambassador for an explanation.

The incident took place days after Moscow demanded an apology from the Netherlands for the alleged beating of a Russian diplomat by Dutch police.

Ties between the two countries have also been aggravated by the detention of 30 Greenpeace activists from a Dutch-flagged ship campaigning against oil drilling in the Arctic.